Increasingly network arrangements are formed from a number of interconnected network regions or domains. The different domains may use different technologies for transport of the service traffic, and may use different technologies to provide fault protection for service traffic in the domain.
In one example of such a situation, carrier Ethernet networks are increasingly being used to provide a switched transport infrastructure based on Provider Bridge and Provider Backbone Bridge technology.
A Provider Bridge network is provided with a loop prevention protocol, such as Rapid Spanning Tree Protocol RSTP, multiple Spanning Tree Protocol MSTP and Ethernet Ring Protection ERP, that also acts as a protection scheme in the network itself. A region in which the routing algorithms and loop prevention packets can be segregated and within which Bridge Protocol Data Units (BPDU) of the loop prevention protocols are propagated is called a domain.
Provider bridge networks protect service traffic from network faults within a domain through distributed loop prevention protocols that calculates a loop free routing topology able to carry the service traffic along a route from the source to the destination of the configured service in response to network faults.
In order to achieve this responsiveness to network faults within a domain, the traffic for a service tagged with the relevant Virtual Local Area Network VLAN tags for the service must be configured on all the network element ports that can be involved in any of the possible packet routes that the loop prevention protocols can calculate.
In the multi-domain network arrangements described above, the loop prevention protocols do not operate between the domains. As a result it is necessary for an inter-domain link to be selected exclusively to carry the service traffic from one domain to another. A failure on this link cannot be protected against.
The present invention seeks to alleviate or ameliorate at least some of the disadvantages of the prior art, and to provide a novel fault protection method and a fault protection apparatus for an inter-domain link of a multi-domain network.